Developer TheFlow has released his Custom PS1 Bubbles tool for the PS Vita: PSOne Loader. PSOne Loader works up to firmware 3.52 included, so if you’re on the latest firmware you’re out of luck for now.

Note that TheFlow originally released this hack a couple days ago, but he found a bug and updated PSOne Loader yesterday. Grab the updated version below if you are having issues.

As a reminder and as we described a few days ago, you’ll need at least one “legit” PS One game installed on your console, from the PSN Store.

What is PSOne Loader?

From the official README:

PSone Loader is a software which allows you to run PSone classic games from the PS Vita Livearea (custom PSone bubbles). It does support custom as well as official PSone games. This software is made of 3 components: The DUMPER, which does dump the PSP and KIRK headers of the ‘simple’ module (DATA.PSP) that is required for the SIGNER program. The SIGNER, which does inject the fake signed custom ‘simple’ module into a PSone game converted as ‘EBOOT.PBP’. The LOADER, which does patch the pops module in order to allow custom converted PSone games and to bypass license verification of official PSone games.

PSOne Loader – Download and Install

You can download PSOne Loader on TheFlow’s bitbucket here.

The Installation is fairly complicated if you’re not familiar with PS Vita scene stuff. Hopefully members of our community will have tutorials shortly in our tutorials section!

From the official site:

1. Base
To setup custom PSone bubbles you'll need to own at least ONE purchased official PSone game. Choose any PSone game, the size of it does not even matter.
You should be able to dump or download the 'EBOOT.PBP' of the choosen game in order to dump the base headers.

2. Dumper
Put the official PSone 'EBOOT.PBP' at 'ms0:/EBOOT.PBP' and run DUMPER on your PSP/pspemu running TN-V. The newest CFW is recommended.
If it could be dumped successfully, you will find a new file at 'ms0:/BASE_HEADERS.BIN'.

3. Signer
You can sign any custom or official PSone game with the signer program. Put a custom PSone 'EBOOT.PBP' and 'BASE_HEADERS.BIN' on your PC near to the signer.exe program.
Then execute signer.exe with these arguments:
'signer BASE_HEADERS.BIN EBOOT.PBP' or 'signer BASE_HEADERS.BIN EBOOT.PBP OUTPUT.PBP'
If it could be signed successfully, the output file does now have the custom 'simple' module injected.

4. Loader
Transfer 'PSVX00000' to your PS Vita, you'll find it at 'PlayStation(R)' in CMA. These are core files of the PSone Loader. Custom PSone bubbles won't start without this loader.

5. Transfer
You can transfer the signed custom PSone EBOOT.PBP to your PS Vita by using CMA (put it in any PSP savedata or even better, in the 'PSVX00000' folder) or by using FTP.
Using VitaShell, PSPFiler or any other programs, create a folder at pspemu directory: /PSP/GAME/DISC_ID, where DISC_ID is the same as in your custom 'EBOOT.PBP'.
This step is important, otherwise the game won't start. Copy your custom 'EBOOT.PBP' to this new folder.

6. App.db
Insert a new entry or modify an existing entry with these strings:

566916785: mba
2593862978: originalpath=ux0:pspemu/PSP/GAME/DISC_ID&selfpath=ux0:pspemu/PSP/GAME/DISC_ID/EBOOT.PBP&discid=DISC_ID&parentallevel=0&gamedataid=&appver=00.00&bootable=1&category=ME
3022202214: vs0:app/NPXS10028/eboot.bin

where DISC_ID is again the DISC_ID of the custom PSone game.

7. Enjoy
Everything has been done and the custom PSone bubble will now work after reboot.

atreyu187 over at psx-place adds:

So for firmware:

• 3.50 and lower only ePSP is needed for install.
• 3.51 Rejuvenate or EML is needed due to write access being blocked in ePSP & ePS1 CEF.
• 3.52 can only be installed via EML with ePSP CEF as Rejuvenate was patched on 3.52 thus stopping native Vita homebrew for VitaShell use.

(And yes, I know, this is a couple days old already, I have to apologize for the lack of updates recently as I was abroad and did not have much time to look at the scene)

Source: TheFlow on twitter